1. Field of the Invention
This invention relates to a therapeutic device and method of administering precisely measured doses of a therapeutic substance via inhalation to pediatric and adult patients. More specifically, the invention relates to a therapeutic device and method of administering inhaled medication which delivers a controlled flow rate to a mouthpiece for administration of medicament to young children, the elderly and other adults with a diminished capacity.
2. Description of Related Art
There is a need for an accurate mechanism for delivering precise drug dosages of inhalable medicaments into the lungs of persons with reduced lung capacity. It is standard medical procedure to treat humans afflicted with pulmonary conditions by administering medicament inhalable into the lungs. For example, asthma is a condition characterized by symptoms wherein the airways of the lungs become narrowed, inflamed and filled with mucous such that the patient experiences wheezing, coughing, and shortness of breath.
Examples of inhalable medicaments used in the treatment of asthma include bronchodilators and anti-inflammatories such as corticosteroids. Other types of inhalable medicaments for different medical conditions include insulin, proteins and polypeptides, enzymes, anticholinergics, antibiotics, antifungals, antivirals, beta-2 agonists, mucolytics and others.
One of skill in the art understands that it is important to control the flow rate of an inhaled medicament so that a defined, consistent, metered (i.e., quantifiable) dose may be administered to the patient. Presently, one of the most popular delivery devices is the pressurized propellant driven metered dose inhaler (“pMDI”) which is typically comprised of a canister containing a mixture of propellants, surfactants, preservatives and one or more active pharmaceutical compounds. The pMDI releases a metered dose of aerosolized medicine upon each actuation. (The contents of the canister of the pMDI and/or the pharmaceutical compounds with or without carriers or excipients are examples of what are sometimes referred to herein as “medicament” or “medicaments.”)
When used frequently, however, pMDIs have certain drawbacks, such as they tend not to permit the administration of defined dosages of the medicament substance for a variety of reasons. Accessories have been developed in an attempt to overcome these drawbacks. Devices called spacers are often used as accessories with pMDIs for the purpose of providing a contained space or holding chamber between the mouth of the patient and the pMDI nozzle from which the medicament is dispensed. Spacers typically are hollow cylinders with open ends. The spacer or holding chamber is used by placing it in the mouth and the patient pursing his or her lips around it, so that a relatively airtight seal is formed between the mouth and the mouthpiece/nozzle of the holding chamber device or spacer. Once such a seal is formed, the pMDI is actuated, releasing aerosolized medicament into the spacer or holding chamber device from which the patient inhales the medicament. Spacers help to capture the gas emitted from a pMDI but do not facilitate inspiration after actuation of the pMDI. It should be noted that pMDIs may be used without a spacer or holding chamber by actuating the pMDI about 2 inches in front of the mouth of the patient, who inhales the aerosol emitted by the pMDI.
An improvement on the spacer device discussed above is a valved holding chamber device, which is similar to a spacer but contains a one-way, low-resistance valve that allows the vaporized or atomized medicament to remain within the body of the chamber until the patient inhales, resulting in the valve opening and permitting the medicament to enter the lungs.
Both spacers and holding chambers have the disadvantage that it is very difficult to ensure that the patient has inhaled the correct dosage of the medicament. Reasons for this include, but are not limited to, the tendency of the medicament to settle via gravity out of the aerosol “mist” to the bottom of the spacer or holding chamber. This settling negatively affects the overall amount of medicament available to inhale, as well as the proportion of “respirable particle size” available to inhale. Respirable particle size refers to the ideal size of inhalable particles; the ideal size is in the range of approximately 1.5 to 2.5 microns. Another disadvantage of the spacers and holding chambers is the patient tends to have difficulties properly timing the release of medicament into the spacer or holding chamber so that the patient inhales at the proper moment.
The aforementioned deficiencies in administering desired dosages of an inhalable medicament led to the inventor's improved holding chamber device disclosed in U.S. Pat. No. 6,085,742 (“the '742 Patent), the disclosure of which is incorporated herein in its entirety by reference. The '742 Patent discloses an intrapulmonary device providing a means for controlling the flow rate so that the inhaled medicament is administered and taken into the patient's lungs in a manner which greatly reduces or even eliminates overdosing and underdosing.
When inhalation devices, including the holding chamber disclosed in the '742 Patent, are used by children, or adults with reduced lung capacity, the accuracy of reported doses and/or amount of drug used in the treatment of a pulmonary disease is unreliable. An overdose or an underdose can have undesirable effects on the patient. A patient can have adverse reactions if too large a dosage of the medicament is inhaled. Conversely, if the patient does not inhale the entire dosage, the medicament may be partially or entirely ineffective to treat the condition for which it was administered.
The device of the '742 Patent, while easy to use and efficient for the administration of medicaments to adults and older children is less reliable when used with children younger than about six years of age. Given that at present about 60% of asthma patients are between the ages of one and five, there is a significant need for a device which will overcome the aforementioned drawbacks of the prior art. A device which can be readily used on patients as young as two years old, or even younger, as well as adults with significantly diminished lung capacity is highly desirable.
It is also highly desirable to have an improved device for readily administering intrapulmonary medicaments to pediatric patients and adults with a diminished capacity for inhaling who are unable to effectively use a pMDI.
Intrapulmonary medication delivery to young children has been attempted by physicians, nurses, respiratory technicians, and other clinicians using many different devices, such as nebulizers, holding chambers, spacers, pMDIs, and dry powdered inhalers (“DPIs”). Currently, the accepted method of delivery using pMDIs for young children of ages five years or less, or to the elderly or others having reduced ability to create sufficient inspiratory flow to use an MDI or pMDI, is to use a spacer device or holding chamber device along with a facemask. Masks usually come in different sizes to accommodate the different ages and/or sizes of patients' faces.
One of the main difficulties in correctly administering inhaled medication results from the inability of some patients to generate consistently low inspiratory flow rates. Most patients inhale at very high inspiratory flow rates in an effort to inhale their entire medicament; this results in a turbulent flow pattern rather than a more desirable laminar flow pattern which provides the best administration of the medicament. Inhaling at a low inspiratory flow rate (30 L/min or less) is equivalent to normal tidal breathing (tidal breathing is a term which describes inhaling and exhaling through the same opening). Many studies in children and especially in children with compromised lung conditions, e.g., Cystic Fibrosis, asthma or other chronic lung diseases (“CLDs”), indicate that low inspiratory flow rates aid in the desirable deep penetration of medication into the pulmonary cavities of the lungs.
Moreover, the proper timing of actuating and inhaling medication from a pMDI is difficult to master for very young children and the elderly. Although spacers and holding chambers are helpful, they do not necessarily result in correct flow rates. In an effort to encourage patients to inhale at correct flow rates, most spacers and holding chambers are equipped with so-called coaching whistles, which actuate at high flow rates to provide an audible signal to the adult or pediatric patient that the flow rate is too high, reminding them to slow down their inspiration. Unfortunately, many children like to hear the whistle, and so intentionally breathe in at a high rate to cause the whistle to sound, thus defeating the purpose of the coaching whistle. These whistle mechanisms are also often used in conjunction with masks and in pMDIs.
Masks, while quite useful, have additional drawbacks. In order for masks with accessory devices to properly work, the masks must have a tight fit on the patient's face. This is not always accomplished with the different masks that are currently on the market. Articles have been published claiming that only extremely tight masks will have a tight enough fit to get medication into the lungs. Masks that leak cause significant problems. Leaked medication decreases effectiveness of the administration of the medication to the patient, and may cause eye irritation as well as resulting in spillage and wasting of medication. Another disadvantage of using a mask is dead space, which is defined as the amount of air that fills the facemask when the mask is placed on the patient's face. Facemask dead space has been measured as being 20-100 mL in volume. The higher the dead space volume, the less medicament reaches the lungs of the patient.
Still another problem with the use of masks is that children tend to find the masks uncomfortable and/or frightening to wear, and therefore do not like having them placed over their mouths and noses. When a mask is used, children tend to have the sensation that they are being smothered, and often resist placement and/or maintenance of the mask on their face.
Still yet another problem with masks is that crying inhibits the child's ability to inhale. In fact, multiple studies have shown that crying infants and toddlers cannot properly inhale medication, leading to insufficient deposition of medication into the lungs.
In spite of the aforementioned drawbacks, masks have been used with nebulizers for at least thirty years. Nebulizers are simple mechanical devices which disperse liquid and/or dry medications into fine particulates which may be inhaled. Nebulizers can be air driven, ultrasonically powered or use vibrating membranes. Although all nebulizers can deliver a superior fine particle dose (as compared to pMDIs) to the mask or traditional mouthpiece of an inhaler, they cannot assure improved penetration to the lungs if a child refuses treatment, cries, or the mask leaks.
Still another problem with nebulizer use is the length of time it takes to inhale medication. It can take anywhere from 10-20 minutes to adequately inhale medication through a nebulizer. As noted above, the difficulty that children have in keeping masks on for this period of time further complicates the use of a nebulizer and increases the time required.
The current invention solves at least some of the problems associated with the administration of intrapulmonary medicaments to young children and adults with diminished lung capacity. An object of the invention is to provide an easily usable, effective device that promotes medication administration compliance, for administering accurate metered dosages to pediatric and other types of patients.